</LineItem>
<LineItem ItemNumber="3">
<Description>Sisters</Description>
<Part Id="715515011020" UnitPrice="29.95" Quantity="4"/>
</LineItem>
</LineItems>
was removed, but I still would like to get Reference from order.

Sorry for violating forum rules that I should create new thread for different oracle version and confusion. I just tested PurchaseOrder on 11.2.0.2 and it produces what you described. And it produces what I described on 10.2.0.5 without error that is raised on 11.2.0.2.